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The single most avoidable
risk factor
for breast cancer is...
...elective abortion.
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The ESTROGEN Connection:
Summary and meta-analysis of epidemiological
evidence of the abortion-breast cancer link:

Explanatory notes:
Each study above is listed by first author's name, year of publication,
and nationality of women studied. On the right-hand side of the figure, the horizontal
line with a central circle, given for each study, represents (on a log scale) the 95%
confidence interval (CI) for the effect of induced abortion on the entire population
studied, with the central circle representing the "point estimate" of
"relative risk" (RR). This RR value represents how many times more likely to
develop breast cancer, in that particular study, is a woman who had at least one induced
abortion, relative to a woman who has not had an induced abortion. For example, in the
1984 French study of Le et al shown above, the point estimate of RR is 1.5, with a 95% CI
that spans from 1.0 to 2.2. In other words, the study found that women who had at least
one abortion were, on average, 50% more likely to develop breast cancer, and that one can
be 95% certain that the increased risk is between 0% and 120%.
Point estimates to the right of the vertical line of unity (RR=1)
indicate increased risk; while those to the left indicate decreased risk. If the 95% CI
does not cross the line of unity, the results are said to be statistically significant.
Narrower 95% CI's denote greater certainty about the RR value, reflecting larger studies
with greater statistical power. Thus, the figure illustrates the fact that of the 33
published worldwide studies, 27 show increased risk, 17 of which are statistically
significant. The pooled average from all the studies combined, calculated by two different
methods, is shown at the bottom. It clearly indicates a significant risk increase
averaging 30 to 40%.
The 1981 study of Pike et al. is limited to women with any abortions
before first full-term pregnancy, the 1988 study of Ewertz and Duffy and the 1996 study of
Wu et al. are limited to women with no children, and the 1957 study of Segi et al. is
limited to women with children.
References
1. Pike et al. (1981) Br J Cancer 43:72-6
2. Brinton et al. (1983) Br J Cancer 47: 757-62
3. Rosenberg et al. (1988) Am J Epidemiol 127-981-9
4. Howe et al. (1988) Int J Epidemiol 18:300-4
5. Laing et al. (1993) J Natl Med Assoc 85:931-9
6. Laing et al. (1994) Genet Epidemiol 11:A300
7. White et al. (1994) J Natl Cancer Inst 86:505-14; Daling
et al. (1994) J Natl Cancer Inst 86:1584-92
8. Newcomb et al. (1996) JAMA 275: 283-7
9. Daling et al. (1996) Am J Epidemiol 144:373-80
10.Wu et al. (1996) Br J Cancer 73:680-6
11.Palmer et al. (1997) Cancer Causes Control 8:841-9
12.Marcus et al. (1999) Am J Pub Health 89:1244-7
13.Lazovich et al. (2000) Epidemiol 11:76-80
14.Moseson et al. (1993) Int J Epidemiol 22:1000-9
15.Segi et al. (1957) GANN 48 (Suppl.):1-63
16.Watanabe & Hirayama (1968) Nippon Rinsho 26:1853-9
(in Japanese)
17.Dvoirin & Medvedev (1978) Meth Breast Cancer Epidemiol
Res, Tallin 1978. USSR Acad Sci pp.53-63 (in Russian)
18.Nishiyama (1982) Shikoku Ichi 38:333-43 (in Japanese)
19-22. Le et al. (1984); Luporsi (1988); Rohan (1988);
Andrieu et al. (1994); in Andrieu et al. (1995) Br J Cancer
72:744-51
23.Hirohata et al. (1985) Natl Cancer Inst Monogr 69:187-90
24.Ewertz & Duffy (1988) Br J Cancer 68:99-104
25.Lipworth et al. (1995) Int J Cancer 61:181-4
26.Rookus & van Leeuwen J Natl Cancer Inst 88:1759-64
27.Bu et al. (1995) Am J Epidemiol 141:S85
28.Talamini et al. (1996) Eur J Cancer 32A:303-10
29.Burany (1979) Jugosl Ginekol Opstet 19:237-47 (Serbo-Croat)
30.Adami et al. (1990) Br J Cancer 62:122-6
31.La Vecchia et al. (1993) Int J Cancer 53:215-9
32.Zaridze et al. (1988) "unpublished" in Ref.
#19 above
33.Melbye et al. (1997) N Engl J Med 336:81-5
34.Rosenberg (1999) NE FL Women's Health v. State of FL,
FL Circuit Ct, 2nd circ., videotape deposition of 11/18/99,
pp.77-8.
35.Clark & Chua (1989) Clin Oncol 1:11-18
36.Brind et al. (1996) J Epidemiol Community Health 50:
481-96
37.Evidence-based Guideline #7 (2000) RCOG Press, pp.29-30
38.Stewart et al. (1993) J Clin Endocrinol Metab 76:1470-6
39.Witt et al. (1990) Fertil Steril 53:1029-36
40.Kunz & Keller (1976) Br J Ob Gyn 83: 640-4
41.MacMahon et al. (1970) Bull Wld Health Org 43:209-21
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